1. Field of the Invention
The present invention relates to a wire electrical discharge machine, and in particular, to a wire electrical discharge machine where it is possible to collect the finished piece (core) by using a manipulator such as a robot.
2. Description of the Related Art
A wire electrical discharge machine processes a workpiece by using a portion of a wire electrode that runs in the vertical direction (up to down direction) between upper and lower wire guide units. The wire electrode is guided through a number of rollers that are fixed to the main body of the wire electrical discharge machine so as to be supplied to the wire guide units equipped with the wire electrical discharge machine. The wire guide units have a wire guide that guides the wire electrode.
Meanwhile, the worktable on which apiece of work is placed moves in the X direction and in the Y direction in accordance with the situation of how the piece of work is to be processed following the instructions from the control unit. The movement in the X direction and the movement in the Y direction are synthesized so that electrical discharge machining processes between the workpiece and the wire electrode that has been supplied between the wire guide units. The workpiece is processed to a predetermined form through electrical discharge machining as the wire electrode and the table move relative to each other.
The wire electrical discharge machine has such a problem that the quality of the finished piece (core) lowers in the case where the finished piece (core) gained by processing the piece of work is left immersed in a process liquid such as water stored in the processing tank. When cemented carbide is left immersed in the process liquid, for example, cobalt comes out from the piece of work, which then becomes friable. When a material such as NAK steel that easily rusts is left immersed, the quality of the finished piece lowers due to the generated rust after machining.
Furthermore, the finished piece left in the processing tank may cause damage to the machine when the finished piece is caught within the wire electrical discharge machine, for example, the finished piece enters into a narrow gap within the processing tank in the wire electrical discharge machine; the finished piece may get caught on the pleated flexible tube, which then breaks; or the finished piece may get caught on a cable, which then disconnects. Moreover, it is difficult to recognize the shape of the finished piece when the finished piece falls within the processing tank, and then it becomes difficult to sort out the finished piece.
In order to solve the problems, Utility Model Registration No. 2504638 discloses a wire electrical discharge machine having such functions that the finished piece is pushed upward until it makes contact with the upper nozzle by means of the strong force of the jetted process liquid and the pressure of the process liquid, and the finished piece is held by a robot arm and then placed in a finished piece container. Utility Model Registration No. 2504638 is characterized by the provision of a sealing member for sealing the gap between the workpiece and the lower nozzle. In addition, Japanese Unexamined Patent Publication S60 (1985)-180726 discloses a wire electrical discharge machine having such functions that a cut out member (finished piece) is suctioned by the instructions from the control unit, and the suctioned finished piece is moved to a container for disposal.
The technology disclosed in Utility Model Registration No. 2504638 is not equipped with a method for recognizing that the finished piece (core) is floating. Therefore, the time when the finished piece (core) floats to a predetermined height cannot be specified, which makes it difficult to determine the point in time when the robot arm is to start operating. In other cases, the hand of the robot arm may fail to catch the finished piece that is not floating sufficiently, or the finished piece (core) may drift away from the hand of the robot arm in the middle of the process of catching the finished piece (core) that is not floating sufficiently with the hand of the robot arm and placing it in a container. When the finished piece has drifted away within the processing tank, it is difficult to collect the finished piece automatically, and therefore, the automated operation of the wire electrical discharge machine must be stopped.
In the technology disclosed in Japanese Unexamined Patent Publication S60 (1985)-180726, it is possible for the cut out member (finished piece) to drift away in the middle of the process of suctioning the cut out member (finished piece) and moving it to the container. In this case as well, it is difficult to automatically collect the cut out member (finished piece) that has drifted away, and therefore, the automated operation of the wire electrical discharge machine must be stopped.